Let-off mechanism of loom

ABSTRACT

A device for maintaining uniform the tension of yarn being drawn to a weaving loom from a yarn beam by detecting the slackness or tension under which the yarns are at all times and for adjusting the tension to a predetermined desired level by braking and restoring the rotational speed of the yarn beam by a hydraulically operated braking system.

11111100 States Patent 1191 1111 3,750,715

Mizuno et a1. Aug. 7, 1973 [54] LET-OFF MECHANISM OF LOOM 3,261,375 7/1966 Berry 139/110 2,526,303 10/1950 Tumer..... 139/100 [751 Inventors Yuk") Mum")? Takes?" 2,529,241 11/1950 131155151 1 66/86 A Oguro, both of Tokyo, Japan I 3,105,524 10 1963 1311166, Jr 139 110 [73] Assignee: Nissan Motor Company, Yokohama FOREIGN PATENTS OR APPLICATIONS Cay, Japan 462,063 10/1968 Switzerland 139/110 732,156 6/1955 Great Britain... [22] 1970 1,292,845 3/1962 France 139/109 [21] Appl. No.: 88,266

Primary Examiner-James Kee Chi [3O] Fol-mg Applicatm Pnomy Data Att0rney-McCarthy, DePaoli and O'Brien Nov. 12. 1969 Japan ..44/90037 52 U S Cl 9 [57} ABSTRACT 13 I110, 66/86 A A device for maintaining uniform the tension of y [51] int. Cl. D03c 49/06 being drawn to a weavin loom from a am beam b 58 Field 61 Search 139/110, 109, 100, g y Y 139/86 66/86 A detecting the slackness or tens1on under whlch the yarns are at all times and for adjusting the tension to a predetermined desired level by braking and restoring [56] References cued the rotational speed of the yarn beam by a hydraulically UNITED STATES PATENTS opemed braking system 2,305,421 12/1942 Herard,1r 139/109 2,305,420 12 1942 Herard, Jr 139 109 6 2 Draw 2,565,386 8/1951 Marcy 139/110 1 LET-OFF MECHANISM OF LOOM This invention relates to a loom and more particularly to a device for hydraulically braking a yarn beam in response to the tension variation of yarns being drawn off from the yarn beam, thereby preventing the tension from deviating from a predetermined desired level.

In the conventional so-called negative let-off mechanism," variations in the tension of yarns being drawn off from the yarn beam are arranged to cause variations in a mechanical braking force applied to rotating shaft of the yarn beam, so that a tensile force of substantially constant magnitude may be imparted to the yarns. However, since the mechanical braking force results from a friction between the rotating shaft and a brake block, it is, in fact, impossible to smoothly control the applied braking force in accordance with the variation in the yarn tension and in some cases the shaft alternates between rotation and stop due to what is called stick phenomenon. Thus, the tension of the yarns greatly varies, leading to difficulties in producing a fabric without quality irregularities.

It is therefore an object of this invention to provide a new and improved hydraulic brake for a yarn beam with a view to overcoming the above-stated disadvantages.

It is another object of this invention to provide a hydraulic brake for a yarn beam that is capable of smoothly controlling a braking force in accordance with the tension variation of yarns so that the tension variation may be reduced to a minimum.

It is a further object of this invention to provide a hydraulic brake for a yarn beam that is simple in construction and economical to manufacture.

In drawings:

FIG. 1 is a schematic diagram showing a hydraulic brake for a yarn beam constructed in accordance with this invention; and

FIG. 2 is an enlarged view, partly in section, of a pump, a valve and a fluid conduit loop shown in FIG. 1.

Referring now to FIG. 1, a schematic view of an embodiment of this invention is shown which generally comprises a yarn beam mounted on a rotating shaft 11 for rotation therewith so as to let off yarns 12 to healds (not shown) by way of a back rest roller 13. The back rest roller 13 is journalled on a first arm 14 secured to a shaft 15 which is rotatably mounted on a frame of a loom (not shown). Also secured to the shaft 15 is a second arm 16 having an abutment 17 formed on its free end. A plunger 18 is mounted for reciprocal movement through bores formed in two spaced brackets 19 and 20 which are provided on the frame. The plunger 18 carries two spring seats 21 and 22 each positioned inside the brackets 19 and 20, one spring seat 21 being secured to the plunger 18. A coil spring 23 is mounted on the plunger 18 between the spring seats 21 and 22. The coil spring 23 brings one end of said plunger into abutting engagement with the abutment 17 so as to swing the second arm 16 in a clockwise direction as viewed in FIG. 1 to thereby tense the yarn.

The rotating shaft 11 to which the yarn beam 10 is secured has secured thereto a gear 24 which is in mesh with another gear 25 secured to the driven shaft 26 of a pump 27. The pump is connected with the fluid conduit loop as will be latter discussed in detail. While in this embodiment the rotating shaft 11 and the driven shaft 26 of the pump 27 are linked to each other by means of a gearing, it is to be understood that other transmitting mechanism such as a chain can be employed.

As is better seen in FIG. 2, the pump 27 is herein shown as of a vane type, though it may be of any other commercially available type such as gear pump or multi-cylinder pump. The rotor-of the pump (not designated) is excentrically mounted in a housing 27' and is rotated by the shaft 11 in the manner already described. The pump 27 has its outlet port 28 connected to a tube-like ball valve 29 positioned in an upright manner. Connected to an inlet port 30 of the pump 27 is a pipe 31 which also is positioned in an upright manner. The upper end of the pipe 31 opens to the air. The valve 29 has an outlet 32 positioned near the top portion thereof, which outlet communicates through a conduit 33 with an inlet 34 provided in the upright pipe 31 so as to cause the flow of working fluid substantially no resistance. The valve 29 comprises a body 35 having a cylindrical shape, a plunger 36 mounted for reciprocal movement through the body 35 and a valve ball 37 hermetically seatable on a valve seat 38 provided at the bottom of the valve body 35. The plunger 36 is provided with upper and lower lands 39 and 40 both in hermetical but sliding contact with the inner wall of the body 35. The upper land 39 is positioned at the upper portion of the body 35 and at an intermediate portion of the plunger 36. The lower land 40 is positioned at the lower end of the plunger 36 and has a depression sized and shaped for receiving the valve ball 37. The lower land 40 is provided with at least one orifice for passing therethrough the working fluid when the valve ball 37 is unseated from the valve seat 38, providing an effective area therebetween.

Turning back to FIG. 1, the plunger 36 is operatively associated with the shaft 15 through a mechanical linkage. The linkage comprises a third arm 41 secured to the integral first and second arms 14 and 16, a rod 42 having one end secured to the third arm 41 and a pivot arm 43 mounted for pivotal movement about a pin 44 mounted on the frame (not shown) and having its free end secured to the other end of the rod 42. The pivot arm 43 has a bore (not numbered) formed therein, through which the plunger 36 is reciprocally movable. The other end of the rod 42 has a threaded portion on which a nut 45 is threadable so as to enable adjustment of the effective length of the rod 42. A coil spring 46 is mounted on the plunger 36 between the pivot arm 43 and the upper land 39 for biasing the plunger 36 toward the valve ball 37 to reduce the effective area between the valve seat 38 and the valve ball 37. This biasing force is normally balanced with the pressure exerted on the lower land 40 by the working fluid flowing through the pump 27.

In operation, when the yarns 12 are slack, the first arm 14 carrying the back rest roller 13 is caused to swing in a clockwise direction as viewed in FIG. 1 by the action of the coil spring 23. When this occurs, the third arm 41 also swings in the same direction as the first arm 14, causing the rod 42 to move downward. Downward movement of the rod 42 causes the pivot arm 43 to swing in a counter-clockwise direction as viewed in FIG. 1, moving the plunger 36 downward by the action of the coil spring 46, so that the valve ball 37 is moved toward the valve closing position. As a result, the amount of operating fluid to be pumped out from the pump 27 is decreased and finally is blocked out when the valve ball 37 decreases, and the pressure flowing through the pump 27 is completely seated on the valve seat 38. This is accompanied by the prohibition of the yarn beam from being rotated by the pump 27. This means that a braking force effected on the rotating shaft acts to reduce the rotational speed of the yarn beam 10. Consequently, the let-off speed of the yarns 12 being drawn off from the yarn beam 10 is decreased. During this operation, however, the yarns 12 continue to be drawn by the healds at a preset drawing speed, so that the once decreased let-off speed will be restored soon, with a resultant proper tension.

On the other hand, when the yarn 12 is under tension exceeding the predetermined proper value, the first arm 14 and the third arm 4] swing in a counterclockwise direction as viewed in FIG. I, causing the rod 42 to move upward. Upward movement of the rod 42 allows the pivot arm 43 to swing in a clockwise direction as viewed in FIG. 1. As a result, the plunger 36 is moved upward, causing the valve ball 37 to move upward to thereby increase the effective area. Consequently, the pressure prevailing within the outlet port 28 of the pump 27 is decreased and the braking force is released. Therefore, the let-off speed of the yarns 12 is increased, rotates, and then the tension experienced by the yarns 12 is reduced to the predetermined proper value.

Meanwhile, the working fluid discharged from the pump 27 into the valve 29 is normally controlled to have a proper flow rate by the effective area with the aid of the force of the coil spring 46 acting upon the valve ball 37. The flow rate in turn controls the rotational speed of the beam 10 and accordingly the yarn tension brake according to this invention utilizes a fluid resistance to effect a braking force on the yarn beam, it' is possible to smoothly control the applied braking force in accordance with the tension variation of a yarn for the purpose of preventing the tension from deviating from a predetermined value.

What is claimed is:

1. A hydraulic brake for controlling tension of yarns being drawn from a yarn beam of a loom, comprising a hydraulic pump adapted to be driven by the yarn beam for pumping out a working fluid, a transmitting mechanism operatively connecting a driven shaft of said pump to a rotating shaft of the yarn beam for transmitting a driving force from the yarn beam to said pump, a liquid conduit loop communicated at its both ends with outlet and inlet ports of said pump for causing the working fluid to circulate therethrough, valve means provided midway of said loop for controlling the flow rate of the working fluid to thereby control the letoff speed of the yarn beam, detecting means for detecting tension variation of the yarns, and a mechanical linkage operatively connected to said pump and detecting means for controlling in response to the detected tension variation the effective area of said valve means through which the working fluid is flown, whereby the let off speed of the yarn beam is controlled in dependence upon the detected tension variation to thereby reduce the tension variation to a minimum.

2. A hydraulic brake according to claim 1, wherein said transmitting mechanism is a gearing.

3. A hydraulic brake according to claim 1, wherein said detecting means includes a first arm secured to a shaft rotatably mounted on a frame of the loom and having a back rest roller joumalled thereon, a second arm secured to the second named shaft and having an abutment provided at its free end, a plunger mounted for reciprocal movement through bores formed in two brackets mounted on the frame, a spring seat secured tosaid plunger between said brackets, a coil spring mounted on said plunger between one of said brackets and said spring seat for bringing one end of said plunger into abutting engagement with said abutment to swing the second named arm together with the first named arm and to tension the yarns, and wherein said mechanical linkage includes a third arm secured to the integral first and second named arms, a rod having one end secured to the third named arm, and a pivot arm mounted for rotational movement about a pin mounted on the frame and having its free end secured to the other end of said rod.

4. A hydraulic brake according to claim 3, wherein said valve means includes a body having a cylindrical shape and positioned in an upright manner, a plunger mounted for reciprocal movement through said body and through a bore formed in said pivot arm and having upper and lower lands in herrnetical but slidable contact with the inner wall of said body, a valve ball positionable on a valve seat formed on the bottom of said body, said upper land being positioned at the upper portion of said body and at an intermediate portion of the second named plunger, said lower land being positioned at the lower end of the second named plunger for receiving said valve ball and having at least one orifice for passing therethrough the working fluid, and a coil spring mounted on the second named plunger between said pivot arm and said upper land for biasing the second named plunger toward said valve ball to reduce the effective area between said valve seat and said valve ball against the pressure of the working fluid pumped out from said pump.

5. A hydraulic brake according to claim 1, wherein said loop includes a passage communicating the outlet of said valve means with the inlet port of said pump.

6. A hydraulic brake according to claim 5, wherein said passage includes an upright pipe connected to the inlet port of said pump and having its upper end open to the air, and a conduit connected its one end to the outlet of said valve means and the other end to the inlet of said pipe, the outlet of said valve means being formed in said body slightly below said upper land. 

1. A hydraulic brake for controlling tension of yarns being drawn from a yarn beam of a loom, comprising a hydraulic pump adapted to be driven by the yarn beam for pumping out a working fluid, a transmitting mechanism operatively connecting a driven shaft of said pump to a rotating shaft of the yarn beam for transmitting a driving force from the yarn beam to said pump, a liquid conduit loop communicated at its both ends with outlet and inlet ports of said pump for causing the working fluid to circulate therethrough, valve means provided midway of said loop for controlling the flow rate of the working fluid to thereby control the let-off speed of the yarn beam, detecting means for detecting tension variation of the yarns, and a mechanical linkage operatively connected to said pump and detecting means for controlling in response to the detected tension variation the effective area of said valve means through which the working fluid is flown, whereby the let-off speed of the yarn beam is controlled in dependence upon the detected tension variation to thereby reduce the tension variation to a minimum.
 2. A hydraulic brake according to claim 1, wherein said transmitting mechanism is a gearing.
 3. A hydraulic brake according to claim 1, wherein said detecting means includes a first arm secured to a shaft rotatably mounted on a frame of the loom and having a back rest roller journalled thereon, a second arm secured to the second named shaft and having an abutment provided at its free end, a plunger mounted for reciprocal movement through bores formed in two brackets mounted on the frame, a spring seat secured to said plunger between said brackets, a coil spring mounted on said plunger between one of said brackets and said spring seat for bringing one end of said plunger into abutting engagement with said abutment to swing the second named arm together with the first named arm and to tension the yarns, and wherein said mechanical linkage includes a thiRd arm secured to the integral first and second named arms, a rod having one end secured to the third named arm, and a pivot arm mounted for rotational movement about a pin mounted on the frame and having its free end secured to the other end of said rod.
 4. A hydraulic brake according to claim 3, wherein said valve means includes a body having a cylindrical shape and positioned in an upright manner, a plunger mounted for reciprocal movement through said body and through a bore formed in said pivot arm and having upper and lower lands in hermetical but slidable contact with the inner wall of said body, a valve ball positionable on a valve seat formed on the bottom of said body, said upper land being positioned at the upper portion of said body and at an intermediate portion of the second named plunger, said lower land being positioned at the lower end of the second named plunger for receiving said valve ball and having at least one orifice for passing therethrough the working fluid, and a coil spring mounted on the second named plunger between said pivot arm and said upper land for biasing the second named plunger toward said valve ball to reduce the effective area between said valve seat and said valve ball against the pressure of the working fluid pumped out from said pump.
 5. A hydraulic brake according to claim 1, wherein said loop includes a passage communicating the outlet of said valve means with the inlet port of said pump.
 6. A hydraulic brake according to claim 5, wherein said passage includes an upright pipe connected to the inlet port of said pump and having its upper end open to the air, and a conduit connected its one end to the outlet of said valve means and the other end to the inlet of said pipe, the outlet of said valve means being formed in said body slightly below said upper land. 